this nuclear tests, unlike the previous one, was safely and perfect conducted at a high level by using a smaller and lighter nuclear armed with high explosive part. >> that claim marks a change about north korea's nuclear program. for years the governments here and in the u.s. have said north korea was some way of having a miniaturize device suitable for use on top of a missile. at least, this test brings that prospect closer. despite last year's successful rocket launch, north korea has yet to develop ballistic missile that could strike the u.s. that the country it says its nuclear weapons programs are targeted at. a miniaturized bomb would emboldened p'yongyang. >> it will give them more confidence that they have a credible deterrent. i personally believe they want a deterrent to keep americans out and to buy them room in which they can operate. >> of the president lee myung- bak held talks. the country's military is on watch for north korea's next move. >> we have strengthened the readiness of our military by increasing the security alert level to level two and we have activated the